Grease compositions



Patented Apr. 14, 1953 GREASE COMPOSITIONS Fred H. Stross and Stanley T.Abrams, Berkeley,

Calif., assigncrs to Shell Development Company, Emeryville, Calif., acorporation of Delaware No Drawing. Application November 27, 1950,Serial No. 197,836

7 Claims.

This invention relates to novel lubricant compositions. Moreparticularly, it is concerned with lubricating compositions comprisinglubricating proportions of an oleaginous liquid and an added agentpossessing a combination of gelling and extreme pressure properties. Thecompositions are characterized by their ability to withstand hightemperatures, excellent resistance to disintegration by water, andantifriction properties at extreme pressures.

There have been disclosed to the art a number of fluid and grease-likecompositions containing sulfurized materials especially for use asextreme pressure lubricants. In most in stances, these compositions havecontained either sulfurized fatty acids or sulfurized fatty oils. Wheregreases are desired particularly for use at high temperatures, suchsulfurized materials show the shortcomings that the compositions areexcessively corrosive and tend to soften or lose their grease-likestructures progressively with increasing temperatures.

It has been proposed to add finely divided disulfides to siliconefluids, said disulfides being derived from metalloids such asmolybdenum, tungsten and titanium. Such compositions may be useful undercertain conditions of operation, but in many instances areunsatisfactory due to the unstable nature of the suspension. Thisunstable character appears to be due to two principal causes. In thefirst place, the disulfides previously used for this purpose, althoughcalled colloidally fine, are not actually believed to be of such highlydispersed nature as to enable them to exist as a true colloidal gel.This is indicated from the fact that the disulfides are derived fromores which have been finely ground to an average dimension of 1 to 50microns. Although these ground ores are subsequently subjected tovarious extraction treatments, it is not believed that this particlesize is appreciably altered. On the other hand, true colloidal gelparticles are defined as those hav ing dimensions of between 0.001 and0.1 micron. Secondly, according to the teachings of the art, thesedisulfides are of a plate-like structure in which it is postulated thatthree layers exist, namely, a middle metalloid layer having on eitherside a layer of sulfur atoms. Structures of this character exhibitlittle attraction between the molecular layers, and, hence, a true gelstructure is not formed when the particles are dispersed in a liquid.

It is an object of the present invention to provide lubricatingcompositions exhibiting improved extreme pressure characteristics. It isanother object of the present invention to provide stable grease-likecompositions especially efiective as extreme pressure lubricants atelevated temperatures. It is a further object of the invention toprovide compositions having the foregoing characteristics and inaddition thereto being comparatively stable to the disintegratinginfiuences of water. The foregoing and other objects will be understoodfrom the following description of the invention.

Now in accordance with the present invention, it has been found thathydrocarbon lubricating oils are provided with grease-like structures bythe dispersal therethrough of colloidal gels of sulfides of metalshaving a water solubility no greater than 0.0005 g. per 100 cc. H2O at20 C. Still in accordance with the present invention, it has been foundthat outstanding members of the present series of greases comprise thosegelled with copper sulfides, since copper sulfides exhibit peculiaroleophilic properties common to sulfides of the hydrogen sulfide groupmetals as compared with other metallic sulfide compounds.

These colloidal particles have sizes varying from 0.01 to 0.3 micron,and usually between 0.01 and 0.1 micron. Electron micrographs indicatethat the particles are three dimensional units showing an agglomeratingtendency which accounts for their stable gel-forming property. It.

has been found that, dependent in part upon the conditions ofpreparation, mixtures of the various types of sulfides are sometimesformed having, for example, arbitrary formulae such as Nl'sSz, which isbelieved to be a mixture of NizS and MS. Other mixtures are known toexist, such as F6384. It is essential that these sulfides be dispersedin the lubricating medium in gel form, the inorganic skeleton of whichis substantially the same as that of an aerogel. While the sulfides maybe prepared by the previously known aerogel process, it is possible toprepare the present compositions without resorting to the expensivedrying operations usually involved in the preparation of an aerogel.However, if the exact steps involved in the preparation of a dry aerogelare to be avoided, they should be such as to permit the formation of agel skeleton structure similar to that of an aerogel.

The lubricating oils useful as the fluid lubricant in the presentcompositions comprise hydrocarbon oils of either natural or syntheticorigin. Preferably, these oils have a viscosity between about SSU" andabout 3,000 SSU at and still more preferably between 300 SSH and 1,000SSU at 100 F. These lubricating oils should have a medium or highviscosity index, preferably between 25 and 150. While the usual sourcefor such oils is from petroleum crudes, other hydrocarbon oils. may beused as well. These include especially polymerized-olefins. andparticularly polymers of normal aliphatic 'olefins having from 6 to 12carbon atoms and copolymers thereof with olefins having from 2. to 6carbon atoms. Polymers having high "viscosity indices and low pourpoints derived from such sources may be prepared by either catalytic ornon-catalytic means. They may. for-example, be prepared by heating theolefins at temperatures between 600 and 900 F. in the absence ofcatalysts or in the presence of-such'catalysts as lead tetraacetate atlower temperatures such-"as 400 F'.-600 F. The clay-type catalysts ofeither natural or synthetic origin such as silica-alumina catalysts. may.be used as well. The advantages of emp oying lubricants.compri'sing..,polymeric olefins. are principally .jthat..of'.qualitycontrol .as ompared with the variable nature of'lubricants obtainedfrom- .naturalscurces. which vary from on oil field to another and evenfrom. one well to another .within a. given field.

The lubricants are, preferably at least moderately refined but, except.when used. as dielectric compositions, need not behighly. refined;however, highly refined lubricating oils. are equally suitable. Whilethe. principal object, of the present invention has been stated'to .bethe production. of grease-like lubricants, another type of composition.contemplated is that of thixotropic gels especially useful. as.cuttingfiuids Qr,,.mo.re particularly. for well-drilling operations.Inthe. latter instance especially, lower molecularweighthydrmcarbonfiuids areespeciallydesirable and particularly. thoseinthekerosene stove. oil .orgas, .oiLboiling; ranges. .Compositionspontainingoils ofi-such low boiling .propertijesihave,beenfound to. exhibitdesirable. thixotropic properties especially .useiul in the operation ofwell-.drillingmechanisms.

'I'he sulfides to be used in the present -compositionsaremetallicsulfidesha ingawatersoluhility less than.0.0005. gram perIOQcQ-pf water at.20. .0. f particular importanceis. the group. ofsulfides. of metals. oi therhydrogensulfide i oupflnamely thosemetals.precipitated .by hydrogen sulfide-as. sulfidesfromtheirsolutions.in0..3l\l'acid; Thelat-. ter groupincludes mercury, lead,copper, bismuth, cadmium,..arseni c, antimonyand tin... .In.addi-- tion.to this group, other. suitable ,sulfldesare thoseof. iron, nickelandcobalt.v

The. essential characteristic of'an. aeroselstructurev and of structuressuitably similar thereto. is that of maximum expansionsoasto permitready dispersalina liquidmediumandthe maintenance of apermanentdispersion thereby... An aerogelispreferably formed by replacing, water.in ahydrogel with alow. boiling. water-miscible solventsuch as ethylalcohol or acetone. heating the resulting organo. gel under pressure tova temperature above the critical temperature of the solvent, and at thispoint flashing off the solvent,'leaying a highly expanded. dry elstructure usually .known. as an aerogel. This structure is opposed to.thestructuresordinarily employed for catalysts which are termedxerogels. gels are generally heated at extremely .high .temperatureswith no effort being taken to maintain an expanded structure; hence,these .products are hard, shrunken structures. ordinarily totally.unsuitable for use. as. grease-forming agents even In the latterinstance, the

. transfer conditions by use of suitable surface-am- .4 though they maybe comminuted to the smallest size attainable-by mechanical means.

Alternative means of preparing suitable gels for use in the presentcompositions comprises forming a hydrogel oi the sulfide, displacingwater with a water-miscible s.clvent...suchasalcohol or acetone. andthen replacing the solvent. with a lubricating oil. Alternatively, thegels may be Originally prepared under anhydrous conditions such as byreaction of an organic acid salt of the desired metal with hydrogensulfide in a nonaqueous medium, such as ethyl alcohol. The an- Ihydrous. gel so formed is then transferred to oil and the surroundinglow boiling medium removed.

greases by especially economical methods. It has been discovered thatthe hydrogels. oicopper S111- fldeffor example) tend to shed water upon,the

addition, .of oil; hence, a, copper sulfidejhydrogel may be directlytransferred to cilandi water re; moved therefrom by simple decantationor distillation underreducedflpressure. The .oil and hydrogelv arepreferably milled to produce. .a finely;

dispersed mixture prior to water removal. v, Still another processforuse in'the'prepara'tion of the present compositions comprises thetransfer of a hydrogel into oil under so-called direct tive agents? Thepresence of surface-active. agents such as high molecular weight aminesand their derivatives enables the production of. the

present compositions. by simple incorporation of the sulfide hydrogel.in oil followed bymilling'to produce a fine dispersion. of thehydrogelinthe oilandlsubsecuent removal of the. vszater,v preferably bydistillation underreducedpressure. Suitable surface-active agents for.usein thislatter process include cationic surface-active materials.

such. as high molecular weightaminesamine salts and quaternary ammonium.compounds. While. the. cationic surface-active. agents. are. especiallypreferred, non-ionic or anionic. agents .may also.

eused. Typical speciesof these. agents-include heptadccylamine,.heptadecylimidazolina amide.

amines of .dieth-ylenetriamine.andoleic acid,,soaps.

such as .ammomum-12-hydroxystearate orlead oleate, soaps, .01: hydroxyamines. such-as, diethanolamine oleate. and glycerinemonostearate-Thecompositions. of the. presentinventionmay:

vary within widelimits. of one. componenttoranother, dependent upon thespecific. use. forwhich the. compositions are to be employed.Preferably, however, the compositions comprise a major amount of thehydrocarbon lubricating .oil,. and a minor amount. of the colloidallydispersedlsuls.

ent, they are ordinarily employed inamountsbe..

tweenabout 2% and 40% by weight of the sulfide or from 1 to 5% based onthe total grease.

Other ingredients may bepresentinthese. compositions including othergrease-forming. agents. such as other inorganic gelling .agents. .ormolecular weight soaps. The former include gels. having structuressimilar to an. aerogeland also similar (in their gelling action). to thesubjectsulfides. These include aerogel-like structures of silica,alumina, magnesia, lime, aluminum silicates, alkaline earth metal oxidesand hydroxides and similar inorganic gelling agents of either natural orsynthetic origin. The natural materials include the swelling-type clayssuch as Wyoming bentonite and hectorite, which have been converted tooleophilic gelling agents by ionexchange with oleophilic cationicsurface active agents as represented by quaternary ammonium bases suchas dimethyldicetylammonium chloride. When these auxiliary gelling agentsare present, they may be used in an amount supplementary to thecolloidal sulfide and may be included in the maximum ratio of saidsulfide of between 5% and 45% by weight of the total composition. Atypical grease of this character includes a composition comprising 70%mineral lubricating oil, silica aerogel and 20% copper sulfide aerogel.The term "aerogel is used throughout the specification to denote thetype of porous gel structure desired rather than the specific method bywhich the gel was prepared.

Typical and illustrative but not limitative preparations of the sulfidegreases are as follows:

EXAMPLE I Fifty-six parts by weight of ferrous sulfate heptahydrate wasdissolved in 100 parts of water made slightly acidic with sulfuric acidto repress hydrolysis. To this solution a solution of 38.7 parts ofhydrogen sulfide dissolved in 434 parts of concentrated aqueous ammoniawas added slowly with stirring. The temperature was maintained at about0 C. After addition of the sulfide solution was completed, the reactionmixture was stirred for an additional minutes. The ferrous sulfide gelwas then filtered, washed with 750 parts of water saturated withhydrogen sulfide and finally with 1,000 parts of methyl alcohol. Thealcogel so prepared was intimately mixed with a refined minerallubricating oil having a viscosity of 300 SSU at 100 F. The mixture washeated to 74 C. and then at a temperature of 50 C. under vacuum for 14hours to remove the last traces of alcohol. The resulting mixture wasthen milled to a grease-like structure and had a concentration of 21% byweight ferrous sulfide based on the total grease.

EXAMPLE I] 408 parts by weight of nickel nitrate hexahydrate wasdissolved in 700 parts of water. To this solution a solution of 190parts of hydrogen sulfide dissolved in 2,140 parts concentrated aqueousammonia were added slowly with stirring. The resulting gel of nickelsulfide so prepared was dehydrated with methanol and dispersed inlubricating oil as described in Example I. The resulting greasecontained 35.7% by weight nickel sulfide.

EXAMPLE III Copper sulfate pentahydrate was dissolved in water to form aconcentrated solution. To this was added just enough concentratedaqueous ammonia to produce a copper-ammonia complex. Hydrogen sulfidewas then bubbled into the solution. The resulting gelatinous precipitatewas thoroughly washed with distilled water. Oil was mixed with thewashed precipitate and the mixture was warmed. As heating progressed, itwas possible to decant all most of the water. Progressive addition ofoil followed by milling and dehydration under vacuum produced a, greasegel containing 23% copper sulfide in oil.

then decanted. The remainder of the alcohol was then removed by heatingon a sand bath. The resulting mixture was milled to produce a greasecontaining 27.3% cupric sulfide.

EXAMPLE V In order to determine the extreme pressure properties of thecompositions prepared as described above, each of the greases wasdiluted with mineral lubricating oil to a gel concentration of 1.5%.These were tested in three-inch spur gears at 3,000 r. p. m. and 45 0.,increasing the loading until scoring of the surfaces occurred. Theextreme pressure loads of the greases were as follows:

Extreme Composition Pressure Load, Lbs.

Mineral lubricating oil 5 Nickel sulfide grease (Example II) 45 Ferroussulfide grease (Example I) 45 Copper sulfide grease (Example IV) 30 Bestcommercial extreme pressure additive l 50 1 Mixture of benzyl disulflde,chlorodibenzyl disuli'lde and chlorinated paraffin wax.

This application is a continuation-in-part of copending application,Serial No. 782,694, filed October 28, 1947, which has matured into U. S.Patent 2,554,222, issued May 22, 1951.

We claim as our invention:

1. A lubricating grease composition comprising a major proportion of ahydrocarbon lubricating oil and as the principal gelling agent therefora minor amount sufiicient to form a grease structure of a colloidallydispersed copper sulfide, said gel being one which has its normal watercontent replaced by said oil.

2. A lubricating grease composition comprising a major proportion of ahydrocarbon lubricating oil and as the principal gelling agent therefora minor amount sufficient to form a grease structure of a colloidallydispersed nickel sulfide, said gel being one which has its normal watercontent replaced by said oil.

3. A lubricating grease composition comprising a major proportion of ahydrocarbon lubricating oil and as the principal gelling agent therefora minor amount sufficient to form a grease structure of a colloidallydispersed iron sulfide, said gel being one which has its normal watercontent replaced by said oil.

4. A lubricating grease composition comprising 55-98% by weight of amineral lubricating oil and 2-45% by weight of a colloidally dispersedmetallic sulfide having a water solubility less than 0.0005 gram per cc.of water at 20 C., said gel being one which has its normal water contentreplaced by said oil.

5. A lubricating grease composition comprising 65-85% by weight of amineral lubricating oil and 15-35% by weight of a colloidally dispersedmetallic grease-forming sulfide having a water solubility less than0.0005 gram per 100 cc. of water at 20 C.. said sulfide having acolloidal ,miiiiliii aeeaova 7 gel structure substantiallythesame asthat of the gel asoriginally formed.

6. A lubricating grease composition comprising a major proportion ofalhydrocarbon' lubricating oil and as a gelling agent therefor'a minoramount sufficient toform agrease structure of a colloidally dispersedmetallic. sulfide vhaving a water solubility less than 0i0005gram per10000. of water Vati20" 'C.,,said'su1fide having a colloidal gelstructure substantially the same as that of they gel as.originally'formed.

'7. A lubricating, grease composition comprising a major proportion of ahydrocarbon lubricating oil and as a gelling agent therefor a minoramount sufficient to form a grease structure of a --colloidallydispersed metallic= sulfide-having a water'solubiIity-less than 0.0005gram per 100 cc.

of water at 20 0., said sulfide having acollo'iclal gel structurewherein thehgelparticles have. dimensions between 0.001 andolmicroneach,the metallic radical of said sulfide being a metal of the group ofmetals precipitated by hydrogen sulflde as sulfides from their solutionsin 0.3N acid, said gel being one which has its normal water contentreplaced by said oil.

FRED I-I. STROSS.

STANLEY T. ABRAMS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,260,625 Kistler' Oct. 28, 1941 2554;222 Stress May 22', I9512,573,650 Peterson Oct.30, 195-1 2,584,085 Stross Jan. 29,1952

4. A LUBRICATING GREASE COMPOSITION COMPRISING 55-98% BY WEIGHT OF AMINERAL LUBRICATING OIL AND 2-4% BY WEIGHT OF A COLLOIDALLY DISPERSEDMETALLIC SULFIDE HAVING A WATER SOLUBILITY LESS THAN 0.0005 GRAM PER100CC. OF WATER AT 20*C., SAID GEL BEING ONE WHICH HAS ITS NORMAL WATERCONTENT REPLACED BY SAID OIL.